The present invention relates to a method and apparatus for controllling the activity of a developing solution against blackening by using a test piece for use in an automatic developer.
In a conventional automatic photographic film developer, the activity of the developing solution which is fatigued or lowered by film blackening, has been maintained to the proper value by some methods as follows.
(a) The replenishment of a supplmentary solution against the blackening is carried out depending on a developed area of the photographic film and a predetermined blackening rate. PA1 (b) The supplementary solution is supplemented depending on a blackened area measured of the photographic film. PA1 (c) The supplementary solution is replenished in a certain period of time corresponding to the measured length of the photographic film to be processed, whose predetermined unit length requires the supplement of a certain volume of the supplementary solution.
The developing solution is also fatigued by oxidation by means of the air, and the like. The degree of the oxidation of the developing solution is different between during and in the absence of the operation of the automatic developer. Hence, in general, the amount of the supplementary solution per unit period of time should be varied during and in the absence of the operation of the developer.
However, as such an activity control of the developing solution is continued, the control errors are accumulated. Accordingly, the activity of the developing solution must be further controlled, for example, twice a day by using a test piece.
In a conventional activity control method of the developing solution against the blackening, the test pieces exposed with the certain light and shade are processed in the standard developing solution and the developing solution whose activity is to be controlled, separately, and then the densities at the predetermined light and shade points of the developed test piece processed in the developing solution to be controlled are compared with those of the test piece processed in the standard developing solution with the naked eye or a densitometer. Then, depending on the difference of these densities, the supplementary solution is added or an exposed useless film is put in the developing solution to be controlled on the basis of the operator's experiences and skill, in order to raise or lower the activity of the developing solution.
In this method, however, the determination of the exact amount of the supplementary solution corresponding to the density difference of the two test pieces is very difficult. Accordingly, in practice, the supplementary solution is usually added in a somewhat smaller amount in a manual manner, and then the activity of the developing solution is measured by using the test piece. When its activity is lower than the standard range, the supplementary solution is added. When its activity is higher than the standard range, i.e. the fresh developing solution is oversupplied, exposed useless films are put therein several times, thereby obtaining a proper activity. However, this operation is very troublesome and involves a lot of time.